In certain applications, bulk products in pulverulent, granular, powdery or other forms are poured in to a generally cylindrical enclosure in successive uniform layers and it is important for these materials to be distributed as uniformly as possible. This is the case, for example, with fluidized-bed lignite driers in which the material must be kept suspended in a fluidizing medium.
In fact, if the lignite is not distributed with the required degree of uniformity, the fluidized bed risks being disturbed in the locations where the distribution is irregular.
Another application is the distribution of pulverulent or powdery materials on the surface of a molten metal bath in a casting ladle. The materials in this case are metal treatment products such as, for example, desulphurization or metal-refining products or products included in the composition of the alloy so as to determine the properties thereof.
To ensure uniform distribution, the document EP-A1-0059411 proposes a distributor consisting of coaxial conical or frustoconical components which ensure distribution of the materials in coaxial frustoconical layers deposited in concentric circles on the surface of a metal bath. The layer thus deposited has, consequently, annular undulations, the width and the depth of which depend on the number of distribution components of the distributor.
Distribution devices consisting of a rotating pouring chute with an adjustable angle of inclination are known. These chutes also deposit the material in concentric circles or, if necessary, in a spiral if the angle of inclination is modified continuously. The layer, consequently, also has undulations in the radial direction. In other words, to ensure a minimum deposition thickness over the entire surface, whatever the device used, more material than necessary must be provided in order to take into account the fact that the thickness in the region of the circular depositions must be greater to guarantee adequate thickness between the annular depositions. In fact, not only does this undulating profile of the layer deposited by these devices conflict with the desired object from a technological or metallurgical point of view, but, moreover, it has an adverse effect on the manufacturing cost of the alloy in the case of casting ladles. These additives are, in fact, very costly materials and care must be taken, therefore, not to add more than is necessary.